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Wednesday, July 5, 2017

Early evening light


I haven't had much time for pictures lately, but I stepped out into the backyard tonight for another try at spider web silk in the early evening light.  Pretty nice!

6 comments:

Ian said...

Stunning! I find it fascinating that the light is not diffracted like one would expect - red-orange-yellow-green-blue-purple - in the center of this image blue is next to orange. I'm wondering what properties of the web are causing this. Have you looked at webs from different species?

Jackie Sones said...

Hi, Ian!

Yes, this is one of the things that fascinates me most about this phenomenon -- the patterns seem so unpredictable! (And they're all so beautiful!)

I have looked at two different types of webs, so that's likely two different species of spiders.

At one point I had read that the colors might have to do with the sticky droplets on the strands, but I have photographed this on the attachment strands, too. (I don't know if the attachment strands also have the droplets?)

If you're curious, here's a link to a document summarizing some of what might be going on:

http://www.dtic.mil/dtic/tr/fulltext/u2/a557824.pdf

Also -- I have noticed that the color patterns are fairly consistent along a strand. If I notice one section that I'm interested in, I can continue to go back to that section to try to capture that particular pattern. [Note: If anyone else is trying this, the movement of the earth/sun matters. That is, you often only have a few minutes in one section of the web. As the angle of light shifts, it changes which strands of the web are lit up.)

I'm still in the very early stages of understanding and appreciating what's going on, but I'm glad to be aware of this phenomenon!

:) Jackie

Ian said...

"Their special optical properties have been achieved by ~136 million years of evolution driven by the need for the web to evade detection by insect prey." I was wondering what the evolutionary advantage was. Thank you for the link. I'm going to start paying a lot more attention to spider webs.

Jackie Sones said...

Hi, Ian,

I was a little confused about that statement. To avoid detection by insect prey, and thereby increase chances of capturing prey, I can see how it would be advantageous for a spider web to be hard-to-see. But I'm not sure how the colorful optical effects displayed when sunlight and the silk interact would play into an evolutionary advantage? Or maybe the authors are trying to say that the properties of the silk and the web have evolved to avoid detection by spider prey, and the optical effects are incidental to those properties?

I suppose you could argue that in general it works well for a web to be hard-to-see, but that it's also risky in that it can be destroyed by larger animals. So perhaps there's a balance between being hard-to-see (better for catching prey) and being detectable (better for ensuring that the web persists)...and that webs have evolved to meet both needs?

Aside from the entire web, it's interesting to think about whether the sections of bright colors along the strands affect the spiders, their prey, or larger animals...or if they're just a by-product of the elements and the situation.

Jackie


Skip Hand said...

Do you see those oval / cigar shapes with your own eyes, or only after photographing it?

Jackie Sones said...

Hi, Skip!

Now that I've had some practice, I *can* see these shapes and colors when looking through the camera lens. I do crop the images after downloading them, to highlight certain strands. I can't see quite as much detail as is revealed in the photo, but yes, I can see the basic shapes and color patterns via the camera. It's quite something!

Interestingly, the bands of colors zip along the silk strands when there's a breeze and the web is moving. It's fascinating to watch the colors moving around among the different strands, but it's easiest to photograph the striped areas when it's calm.

And it's true what's been mentioned, that to see the shapes and stripes as shown in the photographs, the strands need to be slightly out of focus. If the image is sharp, then you might be able to differentiate solid colors along the strands, but the striped details aren't apparent.

Best,

Jackie